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The development of sensitive chromogenic chemosensors for sensing Cu 2+ has been receiving much attention in recent years because of their potential application in clinical biochemistry and the environment studies. Numerous chemosensors have been developed for selective recognition of different species on the basis of host–guest interactions such as hydrogen-bonding, electrostatic force, metal–ligand coordination, hydrophobic and van der Waals force of interactions. The simple and rapid sensing of Cu 2+ ions in biological and environmental systems is desirable and the development of selective and sensitive imaging tools capable of monitoring Cu 2+ ions rapidly has attracted considerable attention. Fluorescent chemosensors have served as useful tool for detecting metal ions owing to their intrinsic sensitivity, selectivity and capacity for rapid, real-time monitoring. Small-molecule fluorescent probes can make use of selective, bio-orthogonal chemistries to report on specific analytes in cells and in more complex biological specimens. This review presents a survey of strategies for using small-molecule fluorescent probes to detect Cu 2+ ions which cover UV to NIR regions such as anthracene, pyrene, quinoline, quinazoline, dansyl, naphthalimide, rhodamine, fluorescein, BODIPY and cyanine dyes. [ABSTRACT FROM AUTHOR]

Copper(II), Cu 2+ , ion plays not only a fundamental role to sustain important physiological processes in living organisms, but also an important environmental pollutant. A large number of chemosensors that employ the chromogenic, fluorogenic or electrochemical properties of molecules have been reported for selective sensing of copper ions with absorbance and emission in the visible region. Nevertheless, most of these chemosensors for Cu 2+ ions have some limitations including low water-solubility, tedious sample treatment, multistep synthetic routes, or unstable detection signal. Therefore, the challenge in the development of light-up chemosensors which are cost-effective, rapid, facile, biocompatible and applicable to the environmental and biological milieus is still a topical issue. In the context of optical sensing of Cu 2+ ion, the unique features offered by transition metal complexes over organic fluorophores have made them a suitable candidate to monitor Cu 2+ ions in biological systems. Encouraged by the importance of Cu 2+ ions, we herein summarize the recent development of transition metal complexes, particularly those of d 6 or d 10 complexes based on rhenium(I), ruthenium(II), iridium(III), zinc(II) and gold(I) complexes, for optical and electrochemical sensing or biosensing applications of Cu 2+ ion. [ABSTRACT FROM AUTHOR]